United Nations weapons inspectors have left Damascus after investigating alleged cases of chemical munitions use.

Their examination included three reported strikes around Damascus in the days after an attack on August 21 which killed an estimated 1,500 people.

A convoy of four UN vehicles carrying the team left a central Damascus hotel on Monday afternoon, heading for Beirut.

Team leader Ake Sellstrom (2nd L) leaves a hotel in Damascus

Meanwhile, another team of 20 UN inspectors who will begin verifying and eliminating Syria's chemical weapons have arrived in Beirut on a private flight from the Netherlands and will head to Damascus later this week.

UN inspectors in Syria at the time of the attack in August have already confirmed that sarin gas was used.

President Bashar al Assad's Western opponents said the inspectors' report left little doubt his forces were to blame for the attack.

But Syrian authorities have denied the accusation, and Russia has said the inspectors' report did not provide irrefutable proof that Assad's forces were responsible.

The inspectors have been clarifying the type of weapons used

Speaking to Kommersant newspaper, Russian Foreign Minister Sergei Lavrov said: "We have presented the evidence we possess ... that led to the conclusion that this was done by the opposition and we have serious suspicions that such attempts continue.”

Lavrov said Russia is prepared to contribute cash to the Organisation for the Prohibition of Chemical Weapons (OPCW) to fund the weapons destruction operation, but did not say how much and suggested Moscow's main contribution would be personnel.

Michael Mann, a spokesman for European Union foreign policy chief Catherine Ashton, told reporters in Brussels the EU is "happy to provide technical and financial support" but is awaiting an official request from OPCW.

A chemical strike in August left hundreds of people injured and dead

The operation to destroy Syria's chemical arsenal will be one of the largest and most dangerous of its kind.

Syria's arsenal is believed to include more than 1,000 tonnes of sarin, mustard gas and other banned chemicals stored at an estimated 45 sites across the country.

The United Nations has launched an urgent appeal for experts to join the mission to destroy the weapons by a target date of mid-2014.

The UN has said it will issue a comprehensive report on its findings next month.